Add 'complex' type

[cdeterman]

As a consequence of issue #67 it is necessary to implement a complex type for the vcl/gpu objects. The interface won't really change as the underlying type is generally hidden from the viewer where for example a gpuMatrix(..., type = "float") results in a fgpuMatrix object there should be a fcgpuMatrix object for the complex type.

This will be complicated by the fact that OpenCL doesn't currently support a complex data type but the work within ViennaCL provides a workaround where the real/imaginary parts are alternated within a vector/matrix. Interfacing this with R objects is the primary goal.

• [ ] cvclMatrix & zvclMatrix
• [ ] cvclVector & zvclVector
• [ ] cgpuMatrix & zgpuMatrix
• [ ] cgpuVector & zgpuVector
• [ ] Re & Im methods